As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminum Association designations in Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association in 2010.
For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated.
Body-in-white consists of the structural components of the automobile, not including closures (e.g. door panels, hood panels, trunk lid panels).
In the production of motor vehicles in particular aluminium alloys the AA5xxx- and AA6xxx-series alloys like 5051, 5182, 5454, 5754, 6009, 6016, 6022, and 6111, have been used to produce automotive structural parts and body-in-white (“BIW”) parts.
There is a demand for the use of aluminium alloys, in particular for formed structural and BIW parts, which are formable and having in particular increased strength after being subjected to a paint bake cycle. In addition, the properties normally required for such parts include a high formability for the forming operation (typically by means of stamping, deep drawing, or roll forming), high mechanical strength after paint baking so as to enabling down gauging thus minimising the weight of the part, good behaviour in the various assembly methods used in motor vehicle manufacturing such as spot welding, laser welding, laser brazing, clinching or riveting, and an acceptable cost for mass production.
International patent application WO-2010/049445-A1 (Aleris) discloses a structural automotive component made from an aluminium alloy sheet product having a gauge in a range of 0.5 to 4 mm, and having a composition consisting of, in wt. %: Zn 5.0-7.0, Mg 1.5-2.3, Cu max. 0.20, Zr 0.05-0.25, optionally Mn and/or Cr, Ti max. 0.15, Fe max. 0.4, Si max. 0.3, and balance is made by impurities and aluminium. The sheet product has been solution heat treatment (SHT) and cooled following said SHT, aged to a yield strength of at least 390 MPa, after aging formed to obtain a formed structural automotive component, then assembled with one or more other metal parts to form an assembly forming a motor vehicle component, and subjected a paint-bake cycle.